Abstract:The single and combined effects of three heavy metal ions (Cu2+, Cd2+, Zn2+) on phosphorus recovery from the simulated phosphorus-rich supernatant in municipal wastewater plant by crystallization of hydroxyapatite (HAP) were investigated. And Visual MINTEQ (Ver3.2) was applied for auxiliary analysis. The results indicated that Cu2+, Cd2+ or Zn2+ could inhibit HAP crystallization for phosphorus removal, and Zn2+ showed the strongest inhibition effect which fitted Monod inhibition model equation with the inhibition constant of 178.0 mg·L?1. The HAP crystallization system could synergistical remove heavy metals, and the order of the removal rate was Cu2+>Cd2+>Zn2+. Joint addition of Cu2+, Cd2+ and Zn2+ could strengthen the inhibition of phosphorus removal and weaken the removal effect of single heavy metal ion. SEM observation showed that the dosing of Cu2+, Cd2+ and Zn2+ led to the loose surface of the products, while they had similar impacts on the morphology of the products. The simulation results of Visual MINTEQ confirmed that Cu2+, Cd2+ and Zn2+ inhibited phosphorus removal by grabbing crystal ions of HAP and formed precipitate with heavy metal impurity, and the order of the impurity content was Cu2+>Cd2+>Zn2+. These results can provide reference for the practical application of HAP crystallization method in phosphorus recovery in urban sewage. Key words:heavy metal/ HAP/ urban sewage/ phosphorus recovery/ Visual MINTEQ.
图1单一存在Cu2+/Cd2+/Zn2+时的磷去除率及重金属对除磷的抑制率 Figure1.Phosphorus removal rate in the presence of Cu2+/Cd2+/Zn2+ and their inhibition rate to phosphorus removal
图3联合投加Cu2+、Cd2+、Zn2+时的磷去除率和重金属对除磷的抑制率 Figure3.Phosphorus removal rate and inhibition rate to phosphorus removal in the presence of mixed Cu2+, Cd2+, Zn2+
表1结晶体系含Cu2+时主要的过饱和物质及相应的Is值 Table1.Major supersaturated substances and their saturation indexes in the crystal system containing Cu2+
过饱和物质
不同Cu2+初始浓度下的Is值
0
5 mg·L?1
10 mg·L?1
15 mg·L?1
20 mg·L?1
25 mg·L?1
HAP
16.874
16.868
16.859
16.849
16.839
16.829
Ca3(PO4)2(beta)*
5.769
5.764
5.758
5.752
5.746
5.739
Ca4H(PO4)3·3H2O
5.158
5.149
5.141
5.132
5.123
5.114
Cu(OH)2
—
2.025
2.141
2.205
2.250
2.284
Cu2(OH)3NO3
—
0.562
1.093
1.397
1.611
1.775
Cu3(PO4)2
—
2.889
3.230
3.421
3.552
3.653
Cu2(OH)3Cl
—
3.575
3.805
3.934
4.022
4.090
CuO (c)*
—
3.640
3.756
3.820
3.865
3.899
注:*表示该物质为同质多晶体,括号内的内容代表同质多晶体的晶型;—表示该物质处于不饱和状态。
过饱和物质
不同Cu2+初始浓度下的Is值
0
5 mg·L?1
10 mg·L?1
15 mg·L?1
20 mg·L?1
25 mg·L?1
HAP
16.874
16.868
16.859
16.849
16.839
16.829
Ca3(PO4)2(beta)*
5.769
5.764
5.758
5.752
5.746
5.739
Ca4H(PO4)3·3H2O
5.158
5.149
5.141
5.132
5.123
5.114
Cu(OH)2
—
2.025
2.141
2.205
2.250
2.284
Cu2(OH)3NO3
—
0.562
1.093
1.397
1.611
1.775
Cu3(PO4)2
—
2.889
3.230
3.421
3.552
3.653
Cu2(OH)3Cl
—
3.575
3.805
3.934
4.022
4.090
CuO (c)*
—
3.640
3.756
3.820
3.865
3.899
注:*表示该物质为同质多晶体,括号内的内容代表同质多晶体的晶型;—表示该物质处于不饱和状态。
下载: 导出CSV 表2结晶体系含Cd2+时主要的过饱和物质及相应的Is值 Table2.Major supersaturated substances and their saturation indexes in the crystal system containing Cd2+
过饱和物质
不同Cd2+初始浓度下的Is值
0
5 mg·L?1
10 mg·L?1
15 mg·L?1
20 mg·L?1
25 mg·L?1
HAP
16.874
16.844
16.814
16.784
16.511
16.726
Ca3(PO4)2(beta)*
5.769
5.748
5.728
5.707
5.573
5.667
Ca4H(PO4)3·3H2O
5.158
5.126
5.094
5.063
4.934
5.000
Cd3(PO4)2
—
4.294
5.184
5.699
6.208
6.339
Cd(OH)2
—
—
—
—
—
0.153
注:*表示该物质为同质多晶体,括号内的内容代表同质多晶体的晶型;—表示该物质处于不饱和状态。
过饱和物质
不同Cd2+初始浓度下的Is值
0
5 mg·L?1
10 mg·L?1
15 mg·L?1
20 mg·L?1
25 mg·L?1
HAP
16.874
16.844
16.814
16.784
16.511
16.726
Ca3(PO4)2(beta)*
5.769
5.748
5.728
5.707
5.573
5.667
Ca4H(PO4)3·3H2O
5.158
5.126
5.094
5.063
4.934
5.000
Cd3(PO4)2
—
4.294
5.184
5.699
6.208
6.339
Cd(OH)2
—
—
—
—
—
0.153
注:*表示该物质为同质多晶体,括号内的内容代表同质多晶体的晶型;—表示该物质处于不饱和状态。
下载: 导出CSV 表3结晶体系含Zn2+时主要的过饱和物质及相应的Is值 Table3.Major supersaturated substances and their saturation indexes in the crystal system containing Zn2+
过饱和物质
不同Zn2+初始浓度下的Is值
0
5 mg·L?1
10 mg·L?1
15 mg·L?1
20 mg·L?1
25 mg·L?1
HAP
16.874
16.814
16.771
16.722
16.703
16.676
Ca3(PO4)2 (beta) *
5.769
5.741
5.720
5.697
5.686
5.672
Ca4H(PO4)3·3H2O
5.158
5.134
5.114
5.093
5.080
5.064
ZnO
—
1.215
1.513
1.685
1.809
1.905
Zn(OH)2 (epsilon) *
—
0.943
1.242
1.414
1.538
1.634
Zn3(PO4)2·4H2O
—
5.267
6.211
6.785
7.166
7.473
Zn5(OH)8Cl2
—
1.749
3.309
4.243
4.910
5.438
注:*表示该物质为同质多晶体,括号内的内容代表同质多晶体的晶型;—表示该物质处于不饱和状态。
过饱和物质
不同Zn2+初始浓度下的Is值
0
5 mg·L?1
10 mg·L?1
15 mg·L?1
20 mg·L?1
25 mg·L?1
HAP
16.874
16.814
16.771
16.722
16.703
16.676
Ca3(PO4)2 (beta) *
5.769
5.741
5.720
5.697
5.686
5.672
Ca4H(PO4)3·3H2O
5.158
5.134
5.114
5.093
5.080
5.064
ZnO
—
1.215
1.513
1.685
1.809
1.905
Zn(OH)2 (epsilon) *
—
0.943
1.242
1.414
1.538
1.634
Zn3(PO4)2·4H2O
—
5.267
6.211
6.785
7.166
7.473
Zn5(OH)8Cl2
—
1.749
3.309
4.243
4.910
5.438
注:*表示该物质为同质多晶体,括号内的内容代表同质多晶体的晶型;—表示该物质处于不饱和状态。
下载: 导出CSV 表4联合投加Cu2+、Cd2+、Zn2+各25 mg·L?1时所有的过饱和物质及相应的Is值 Table4.All supersaturated substances and their saturation indexes with joint addition of 25 mg·L?1 Cu2+, Cd2+ and Zn2+
过饱和物质
Is值
过饱和物质
Is值
Cu2(OH)3Cl
4.168
HAP
16.478
Ca3(PO4)2 (am1) *
1.678
CuO(am) *
3.007
Ca3(PO4)2 (am2) *
4.449
CuO(c) *
3.857
Ca3(PO4)2 (beta) *
5.540
ZnO
1.905
Ca4H(PO4)3·3H2O
4.868
Zn(OH)2 (am) *
0.673
CaHPO4
0.140
Zn(OH)2 (beta) *
1.400
Cd3(PO4)2
6.177
Zn(OH)2 (delta) *
1.559
Cd(OH)2
0.026
Zn(OH)2 (epsilon) *
1.634
Cu(OH)2
2.242
Zn(OH)2 (gamma) *
1.424
Cu2(OH)3NO3
1.939
Zn2(OH)3Cl
0.071
Cu3(PO4)2
3.640
Zn3(PO4)2·4H2O
7.346
Cu3(PO4)2·3H2O
1.910
Zn5(OH)8Cl2
5.427
注:*表示该物质为同质多晶体,括号内的内容代表同质多晶体的晶型;—表示该物质处于不饱和状态。
过饱和物质
Is值
过饱和物质
Is值
Cu2(OH)3Cl
4.168
HAP
16.478
Ca3(PO4)2 (am1) *
1.678
CuO(am) *
3.007
Ca3(PO4)2 (am2) *
4.449
CuO(c) *
3.857
Ca3(PO4)2 (beta) *
5.540
ZnO
1.905
Ca4H(PO4)3·3H2O
4.868
Zn(OH)2 (am) *
0.673
CaHPO4
0.140
Zn(OH)2 (beta) *
1.400
Cd3(PO4)2
6.177
Zn(OH)2 (delta) *
1.559
Cd(OH)2
0.026
Zn(OH)2 (epsilon) *
1.634
Cu(OH)2
2.242
Zn(OH)2 (gamma) *
1.424
Cu2(OH)3NO3
1.939
Zn2(OH)3Cl
0.071
Cu3(PO4)2
3.640
Zn3(PO4)2·4H2O
7.346
Cu3(PO4)2·3H2O
1.910
Zn5(OH)8Cl2
5.427
注:*表示该物质为同质多晶体,括号内的内容代表同质多晶体的晶型;—表示该物质处于不饱和状态。
下载: 导出CSV 表5联合投加Cu2+、Cd2+、Zn2+各25 mg·L?1时主要元素在液相和固相中的分布 Table5.Distribution of main elements in liquid and solid phases with joint addition of 25 mg·L?1 Cu2+, Cd2+ and Zn2+
PENG L H, LU X W, DAI H L, et al. A comprehensive review of phosphorus recovery from wastewater by crystallization processes[J]. Chemosphere, 2018, 197: 768-781.
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USTUM G E. Occurrence and removal of metals in urban wastewater treatment plants[J]. Journal of Hazardous Materials, 2009, 172(2/3): 833-838.
MADSEN H E L. Influence of foreign metal ions on crystal growth and morphology of brushite (CaHPO4, 2H2O) and its transformation to octacalcium phosphate and apatite[J]. Journal of Crystal Growth, 2008, 310(10): 2602-2612.
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ZHOU Z, HU D L, REN W C, et al. Effect of humic substances on phosphorus removal by struvite precipitation[J]. Chemosphere, 2015, 141: 94-99.
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WANG J, SONG Y, YUAN P, et al. Modeling the crystallization of magnesium ammonium phosphate for phosphorus recovery[J]. Chemosphere, 2006, 65(7): 1182-1187.
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MURYANTO S, BAYUSENO A P. Influence of Cu2+ and Zn2+ as additives on crystallization kinetics and morphology of struvite[J]. Powder Technology, 2014, 253: 602-607.
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DAI H L, TAN X W, ZHU H, et al. Effects of commonly occurring metal ions on hydroxyapatite crystallization for phosphorus recovery from wastewater[J]. Water, 2008, 10(11): 1619-1630.
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School of Energy and Environment, Southeast University, Nanjing 210096, China Received Date: 2020-07-18 Accepted Date: 2020-11-27 Available Online: 2021-03-24 Keywords:heavy metal/ HAP/ urban sewage/ phosphorus recovery/ Visual MINTEQ Abstract:The single and combined effects of three heavy metal ions (Cu2+, Cd2+, Zn2+) on phosphorus recovery from the simulated phosphorus-rich supernatant in municipal wastewater plant by crystallization of hydroxyapatite (HAP) were investigated. And Visual MINTEQ (Ver3.2) was applied for auxiliary analysis. The results indicated that Cu2+, Cd2+ or Zn2+ could inhibit HAP crystallization for phosphorus removal, and Zn2+ showed the strongest inhibition effect which fitted Monod inhibition model equation with the inhibition constant of 178.0 mg·L?1. The HAP crystallization system could synergistical remove heavy metals, and the order of the removal rate was Cu2+>Cd2+>Zn2+. Joint addition of Cu2+, Cd2+ and Zn2+ could strengthen the inhibition of phosphorus removal and weaken the removal effect of single heavy metal ion. SEM observation showed that the dosing of Cu2+, Cd2+ and Zn2+ led to the loose surface of the products, while they had similar impacts on the morphology of the products. The simulation results of Visual MINTEQ confirmed that Cu2+, Cd2+ and Zn2+ inhibited phosphorus removal by grabbing crystal ions of HAP and formed precipitate with heavy metal impurity, and the order of the impurity content was Cu2+>Cd2+>Zn2+. These results can provide reference for the practical application of HAP crystallization method in phosphorus recovery in urban sewage.